Clinical & Hospital Pharmacy

Anticoagulation Risk Calculator

Scores stroke risk (CHA₂DS₂-VASc) and bleeding risk (HAS-BLED) in atrial fibrillation, with a DOAC dosing reference.

CHA₂DS₂-VASc score

2of 9 points

Ischaemic stroke 2.2% / year · Class I (Strong Recommendation)

Recommendation

Class I (Strong Recommendation)

High Risk (≥ 2 clinical risk factors). Oral anticoagulation (DOAC preferred over Warfarin) is strongly recommended.

Stroke risk factors

Tick every factor the patient has. The two age bands are mutually exclusive.

C — Congestive heart failure / LVEF ≤ 40%+1H — Hypertension (resting SBP > 140 mmHg or treated)+1A₂ — Age ≥ 75 years+2D — Diabetes mellitus (oral agent or insulin)+1S₂ — Prior stroke, TIA or systemic thromboembolism+2V — Vascular disease (prior MI, PAD, aortic plaque)+1A — Age 65–74 years+1Sc — Female sex (sex category)+1

Try an example patient

Working

Points from each ticked factor.

H — Hypertension (resting SBP > 140 mmHg or treated)+1

A — Age 65–74 years+1

Total1 + 1 = 2points

Net clinical benefit

Annual event rates for both scores side by side.

Annual stroke risk · CHA₂DS₂-VASc 22.2%

Annual major bleed · HAS-BLED 21.9%

Modifiable bleeding risks to act on

Control systolic BP (< 140 mmHg resting).

Deprescribe unnecessary NSAIDs, Aspirin, or antiplatelets.

Counsel on reducing alcohol intake (< 8 units/week).

If on Warfarin, target TTR > 70% or switch to a DOAC.

CHA₂DS₂-VASc (0–9 points)

C 1 + H 1 + A₂ (age ≥ 75) 2 + D 1 + S₂ (stroke/TIA) 2 + V 1 + A (age 65–74) 1 + Sc (female) 1

Men: 0 = no OAC (Class III), 1 = consider OAC (Class IIa), ≥ 2 = OAC recommended (Class I). Women: 1 (sex alone) = no OAC, 2 = consider OAC, ≥ 3 = OAC recommended.

Annual ischaemic stroke rate by score
Score	0	1	2	3	4	5	6	7	8	9
% / yr	0.2	0.6	2.2	3.2	4.8	7.2	9.7	11.2	12.5	15.2

HAS-BLED (0–8 points)

H + A (renal) + A (liver) + S + B + L + E + D (drugs or alcohol) — 1 point each

0–1 = low, 2 = moderate, ≥ 3 = high bleeding risk.

Annual major bleeding rate by score
Score	0	1	2	3	4	5	6	7	8
% / yr	0.9	1.1	1.9	3.7	8.7	12.5	14	15	18

References

2024 ESC Guidelines for the Management of Atrial Fibrillation. Eur Heart J. 2024. Recommends oral anticoagulation in non-valvular AF for men with CHA₂DS₂-VASc ≥ 2 and women with CHA₂DS₂-VASc ≥ 3 (Class I). DOACs preferred over VKAs.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of AF. Circulation. 2023. Reinforces that high bleeding risk scores (HAS-BLED ≥ 3) should prompt risk factor modification rather than withholding anticoagulation.

Pisters R, et al. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation. Chest. 2010;138(5):1093-1100.

Common questions

No. A HAS-BLED of 3 or more flags patients who need their modifiable risks corrected — blood pressure, NSAIDs or antiplatelets, alcohol, labile INR — and closer follow-up every 3–6 months. It is not on its own a reason to withhold OAC.

Female sex adds a point but is a risk modifier rather than an independent risk factor: a woman whose only factor is her sex (score 1) has a low stroke risk. That is why the threshold for OAC is one point higher in women.

No. Age 65–74 scores 1 and age ≥ 75 scores 2; a patient is in one band only. Ticking one clears the other.

Creatinine clearance calculated with the Cockcroft-Gault equation (actual body weight), which is what the DOAC trials and labels used. eGFR can overestimate clearance in older, lighter patients and lead to overdosing.

Aspirin prevents far fewer AF-related strokes than an anticoagulant, while its major bleeding risk — especially in older patients — is similar to a DOAC. Guidelines therefore recommend against antiplatelet monotherapy for this purpose.

About these scores

In non-valvular atrial fibrillation (AF), the decision to start an oral anticoagulant (OAC) weighs the yearly risk of ischaemic stroke against the risk of major bleeding. CHA₂DS₂-VASc estimates the first, HAS-BLED the second.

DOACs — direct oral anticoagulants: apixaban, rivaroxaban, dabigatran, edoxaban — are recommended in preference to vitamin K antagonists (warfarin) for non-valvular AF. Aspirin alone is not recommended for stroke prevention in AF: it is less effective with a similar bleeding risk.

How to use it

Score stroke risk: OAC is indicated at CHA₂DS₂-VASc ≥ 2 in men or ≥ 3 in women

Score bleeding risk to find modifiable factors — hypertension, NSAIDs, alcohol — without withholding OAC

Choose a DOAC and check its renal, age and weight dose-reduction criteria

Keep in mind

These scores are decision aids. Always weigh individual bleeding risk, renal function, adherence and the patient's own preferences before starting OAC.

The scores apply to non-valvular AF — not to mechanical heart valves or moderate–severe mitral stenosis.

Calculate CrCl with Cockcroft-Gault for DOAC dose decisions, not eGFR.

Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy